Not being a shill here but I've had great results buying from Diver's Den. While they don't 'QT' the fish, they are treated and observed for a few weeks before being shipped. I also like that they ship in 1.024-5 water.
This is going to sound like heresy, but I also think that most home QT's cause as much damage as good. You basically stick a fish that's just been through the most stressful experience imaginable into a ten gallon tank with no live rock and a back filter (ammonia can build up quickly with such weak biology). You then put it through chemotherapy (high power antibiotics, copper, TTM, etc.). Most don't have ATO's so you likely have swings in salinity. After six weeks of this, you move it into yet another environment where it suddenly has to compete for food, hiding places, etc. The next day, fish is upside down sticking to your overflow.
I'm not saying that QT can't be done right but I would be willing to bet that most QT's closely mimic what I described. If that's you then you're better off just doing a quick acclimation and putting the fish directly into your tank.
And for the close of this rant...wild fish have to deal with every disease we see in this hobby. The strongest and healthiest have an immune system that can fight off all of these diseases and they live to a ripe old age. Once again, I'm not against proper healthy QT but the best thing you can do for your fish is to provide a truly healthy and save environment for your fish in your DT. Feed quality foods, manage water quality carefully, understand compatability, etc.
Rant over and sorry for the long post.